Difference between revisions of "Surface Water Routing:Overland Boundary Conditions"
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Overland boundaries may be used to model coastal storm surges or areas around a standing water body. In essence, GSSHA will take a map of the boundary conditions (constant slope, constant head, or time-varying head) and apply that condition at the beginning of each time step. | Overland boundaries may be used to model coastal storm surges or areas around a standing water body. In essence, GSSHA will take a map of the boundary conditions (constant slope, constant head, or time-varying head) and apply that condition at the beginning of each time step. | ||
| − | Setting up overland boundaries consists of 1) creating an index map describing the boundary condition of all cells, 2) creating the overland boundary mapping table, 3) if needed, creating the time series index mapping table, 4) if needed, creating the time series file, 5) adding appropriate project file cards. | + | Setting up overland boundaries consists of 1) creating an index map describing the boundary condition of all cells, 2) creating the overland boundary mapping table, 3) if needed, creating the time series index mapping table, 4) if needed, creating the time series file, 5) if needed, create the rating curve index mapping table 6) if needed, create the rating curve input file 7) adding appropriate project file cards. |
==Index Map== | ==Index Map== | ||
Revision as of 18:59, 19 November 2012
Contents
Overland Boundaries
Overland boundaries may be used to model coastal storm surges or areas around a standing water body. In essence, GSSHA will take a map of the boundary conditions (constant slope, constant head, or time-varying head) and apply that condition at the beginning of each time step.
Setting up overland boundaries consists of 1) creating an index map describing the boundary condition of all cells, 2) creating the overland boundary mapping table, 3) if needed, creating the time series index mapping table, 4) if needed, creating the time series file, 5) if needed, create the rating curve index mapping table 6) if needed, create the rating curve input file 7) adding appropriate project file cards.
Index Map
The index map is a standard index map. All cells must have a value. Usually, all cells will begin as a uniform value and then changes along the boundaries will be done to create specific instances of boundary conditions. Each specific instance of a boundary condition will have a unique ID.
Overland Boundary Mapping Table
The overland boundary mapping table is very similar to the standard style mapping tables. The table has two parameters, with the meaning of the second parameter dependent upon the first. The first parameter is a boundary type code. The second parameter is a value corresponding to the meaning of the boundary type code.
| Boundary Type Code | Second Parameter Meaning |
|---|---|
| 0 (Normal cell) | Put 0.00 |
| 1 (Specified slope) | Slope (e.g. 0.001) |
| 2 (Constant specified head) | Constant water surface elevation of water in the cell |
| 3 (Time variable specified head) | Time series index of water surface elevation |
| 4 (Hydrograph - cfs) | Time series index of hydrograph |
| 5 (Hydrograph - cms) | Time series index of hydrograph |
| 6 (Rating curve - head difference -cms) | Table of difference in stage verses discharge rating curve |
| 7 (Rating curve - upstream depth-cms) | Table of depth verses discharge rating curve |
| 99 (Receiving cell - Downstream cell for rating curve structure ) | Put 1 |
The overland boundary table identifier is OVERLAND_BOUNDARY.
Time Series Index Mapping Table
The overland boundary table refers to a time series index table. This table links a unique ID value to a time series name. This table is not in the standard table format. It does not link to an index map, nor does it have any descriptions. The format is shown in the following example.
TIME_SERIES_INDEX NUM_IDS ## ID Time Series Name (text line) [##] “name here” [##] “name here” … [##] “name here”
The names referred to are defined in the individual time series.
Time Series Files
Time series files contain as many time series as desired. Time series files are defined in the GSSHA wiki site. Two examples of time series are shown below.
GSSHA_TS levee_breach RELATIVE 0 0 0 0 0 140.0 0 0 1 0 0 139.5 END_TS GSSHA_TS storm_surge ABSOLUTE 2005 8 26 4 0 2.4 2005 8 26 8 0 3.2 2005 8 26 13 0 3.4 2005 8 27 0 0 2.4 END_TS
Project Cards
To turn on the overland boundary process, include the card
OV_BOUNDARY
in the project file. To include the time series files, include the card
TIME_SERIES_FILE "filename.ext"
in the project file. This card may be repeated for as many time series files as are needed.
Example
Using the two time series defined above, the mapping tables would look like this:
INDEX_MAP "bdy.idx" "bdy" TIME_SERIES_INDEX NUM_IDS 2 ID Time series name 1 "levee_breach" 2 "storm_surge" OVERLAND_BOUNDARY "bdy" NUM_IDS 3 ID desc… bdy_type bdy_param 1 normal cells 0 0.00 2 specified slope 1 0.001 3 storm surge 3 2
Assuming the time series are in a file called 'flood.ts', the project file would have the following cards:
OV_BOUNDARY TIME_SERIES_FILE "flood.ts"
GSSHA User's Manual
- 5 Surface Water Routing
- 5.1 Channel Routing
- 5.2 Overland Flow Routing
- 5.3 Channel Boundary Conditions
- 5.4 Overland Boundary Conditions
- 5.5 Embankments
- 5.6 Overland/Channel Interaction
- 5.7 Introducing Discharge/Constituent Hydrographs
- 5.8 Overland Routing with Snow
- 5.9 Overland Routing with BMPs
